If Di amount of drug is administered as loading dose then (FxDi ) amount of drug will be absorbed in the body where F is the oral bioavailability of drug

Therefore, F Di = CSS x Vd

Calculation of maintenance dose

The Di dose will raise the plasma concentration of the drug to CSS and will reach the peak. After CSS is reached the elimination rate from the body will be maximum and the elimination rate will be KE x Vd x CSS. An ideal maintenance dose will supply drug at a rate in which the drug is eliminated from the body.

Therefore, the rate of delivery from the maintenance dose = elimination rate (Routput)